How to update environment to new version of Ext?

How to update environment to new version of Ext?

I have a workspace for Ext JS 4.2. I have a custom theme in there, in addition to a couple of small test apps.

Now I want to upgrade to a nightly beta of 4.2.1, to test if a particular bug is fixed. What is the correct procedure for upgrading an existing workspace to a new version of Ext, or perhaps to make it so I can just test with the new version?

I tried pointing editing my sencha.cfg file and pointing it to the directory where I unzipped the new version, but building the app failed when it found some inconsistency in the themes.

Is my only option to create a new workspace, and migrate my apps and custom themes to the new workspace?